The making of a mushroom: Mitosis, nuclear migration and the actin network (original) (raw)
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2019
The nuclear behavior in the developing stages in basidium (Sporophore) of homothallic basidiomycete Volvariella volvaceae (Bull, ex. Fr). was studied with light microscopy collected from natural habitat i.e. rice/paddy straw from Hooghly District, West Bengal. Occurrence, distribution and their patterns of division in both vegetative and reproductive structures i.e., mycelium (length 45.34 ± 1.393 µ and breadth of 13.69 ± 1.047 µ respectively with multinucleate 15-35 nuclei in diffusely scattered condition) and basidium (Mean length and breadth of probasium was found to be 36.31 ± 1.88 µ and 12.41 ± 0.798 µ respectively with 8 diving nuclei) in Volvariella have been found to be unique. A high frequency of migrating nuclei was accounted in the vegetative mycelia which divide by different means and planes. At developing probasidium 11 chromosomes (10 bivalents and 1 univalent) could be found out in metaphase I. The migrating nuclei in the probasidium are always constricted in form with limited numbers and divide also in more than one plane. The haploid complement of the mature basidium could show 4 compact nuclei ready to enter the developing basidiospores. The preponderance of meiosis with the resultant post-karyotic nuclei are enclosed within nuclear envelope could form post-meiotic mitosis which is a peculiar phenomenon in the present study from cryptogamic karyological point of view. These added features clearly demand the input by other molecular tools which could definitely underpin a full and complete overview of the fungal chromosomes to bridge the gaps at our three conceptual levels of fungal genomics: Genome, chromosome and í µí°·í µí±í µí°´.
Scientific Reports
The developmental biology underlying the morphogenesis of mushrooms remains poorly understood despite the essential role of fungi in the terrestrial environment and global carbon cycle. The mushroom Coprinopsis cinerea is a leading model system for the molecular and cellular basis of fungal morphogenesis. The dikaryotic vegetative hyphae of this fungus grow by tip growth with clamp cell formation, conjugate nuclear division, septation, subapical peg formation, and fusion of the clamp cell to the peg. Studying these processes provides many opportunities to gain insights into fungal cell morphogenesis. Here, we report the dynamics of five septins, as well as the regulators CcCla4, CcSpa2, and F-actin, visualized by tagging with fluorescent proteins, EGFP, PA-GFP or mCherry, in the growing dikaryotic vegetative hyphae. We also observed the nuclei using tagged Sumo proteins and histone H1. The five septins colocalized at the hyphal tip in the shape of a dome with a hole (DwH). CcSpa2-EG...
American journal of botany, 2004
Phylogenetic studies of yeasts rely on an extensive molecular and biochemical data set, but structural characters are scarce. Details of mitosis in yeasts have been studied with transmission electron microscopy and immunofluorescence. Of these two methods immunofluorescence is faster and easier and yields sufficient detail for cytological comparisons. Only three basidiomycetous yeasts have been studied thus far with immunofluorescence. Mitosis in budding cells of ascomycetous yeasts occurs in the parent, while in basidiomycetous yeasts, except in Agaricostilbum pulcherrimum, it occurs in the bud. Mitosis in additional yeasts in the Agaricostilbomycetidae of the Urediniomycetes was observed using immunofluorescence localization of freeze-substituted material. In Stilbum vulgare, mitosis occurred in the parent, but in Bensingtonia yuccicola it occurred in the bud as in most other basidiomycetous yeasts. Stilbum vulgare also had predominantly binucleate yeast cells. Nuclear small subun...
Molecular Microbiology, 1997
Nuclear migration and nuclear positioning are fundamental processes in all eukaryotic cells. They are easily monitored during hyphal growth of filamentous fungi. We expressed the green fluorescent protein (GFP) as a fusion protein with the putative nuclear localization domain of the transcriptional activator stuA in nuclei of Aspergillus nidulans and visualized these organelles in living cells. Nuclear staining was observed in interphase nuclei but not during mitosis. Nuclear division, nuclear migration, septum formation and branching were analysed with time-lapse video microscopy during hyphal extension. Hyphae elongated at 0.1-1.2 m min ¹1 and nuclei moved with similar speeds towards the hyphal tip until they had reached a defined position. An individual regulation of nuclear mobility in a given hyphal compartment was observed. Some representative movies are available on the Internet (http:/ /www.blacksci.co.uk/products/journals/molextra.htm). Nuclear positioning was also studied at the molecular level. The ApsA protein, which regulates nuclear migration, was localized at the cytoplasmic membrane in germlings and hyphae by immunofluorescence and GFP tagging. A model of nuclear migration, nuclear positioning and the role of ApsA is presented.
Nuclear Dynamics and Cell Growth in Fungi
Fungal systems provide an especially excellent model for understanding the fundamentals of nuclear behavior in all cells. Fungal nuclei are highly dynamic organelles capable of long-range movements and rapid changes in gene expression as well as large-scale genomic alterations to adapt to their environment. Nuclei are strategically and actively positioned to facilitate their interactions with other cellular components and contribute to successful growth and reproduction of the organism. Each nucleus is a potential unit of selection, and yet different genotypes may come together in one cell to increase the fitness of multinucleate organisms as a whole. Despite the rich history of research into fungal nuclear dynamics, it is clear that we still have much to learn and there are numerous avenues of investigation that have yet to be thoroughly explored.
Eukaryotic Cell, 2010
Neurospora crassa macroconidia form germ tubes that are involved in colony establishment and conidial anastomosis tubes (CATs) that fuse to form interconnected networks of conidial germlings. Nuclear and cytoskeletal behaviors were analyzed in macroconidia, germ tubes, and CATs in strains that expressed fluorescently labeled proteins. Heterokaryons formed by CAT fusion provided a rapid method for the imaging of multiple labeled fusion proteins and minimized the potential risk of overexpression artifacts. Mitosis occurred more slowly in nongerminated macroconidia (1.0 to 1.5 h) than in germ tubes (16 to 20 min). The nucleoporin SON-1 was not released from the nuclear envelope during mitosis, which suggests that N. crassa exhibits a form of “closed mitosis.” During CAT homing, nuclei did not enter CATs, and mitosis was arrested. Benomyl treatment showed that CAT induction, homing, fusion, as well as nuclear migration through fused CATs do not require microtubules or mitosis. Three ropy mutants (ro-1, ro-3, and ro-11) defective in the dynein/dynactin microtubule motor were impaired in nuclear positioning, but nuclei still migrated through fused CATs. Latrunculin B treatment, imaging of F-actin in living cells using Lifeact-red fluorescent protein (RFP), and analysis of mutants defective in the Arp2/3 complex demonstrated that actin plays important roles in CAT fusion.
Nuclear migration in fungi – different motors at work
Research in Microbiology, 2000
Lower fungi such as Saccharomyces cerevisiae and Aspergillus nidulans are ideal organisms for studying the molecular biology underlying nuclear migration in eukaryotic cells. In this review, the role of different motor proteins such as dynein, kinesin and myosin will be discussed.
Fungal nuclear behavior analysed by ultraviolet microbeam irradiation
Cell Motility and The Cytoskeleton, 1986
During hyphal tip growth in the fungus Basidiobolus magnus, nuclei normally maintain a constant distance from the advancing cell apex by continuously migrating forward. It is not known whether the mechanism that produces nuclear movement also mediates nuclear positioning, or whether these two processes are under separate control. By irradiating small cytoplasmic regions with an ultraviolet microbeam, the coordination between movement and positioning could be disrupted. Regardless of the distance of the target from the nucleus, anterior irradiations (those ahead of the nucleus) caused the nucleus to stop or move backwards, whereas posterior (behind the nucleus) irradiations caused an acceleration in the nuclear velocity. The nucleus retained its ability to move following irradiation, so there was only loss of control over normal positioning. These results suggest that movement and positioning are mediated by different mechanisms. Quantitative microtubule analysis demonstrated that microtubules in the target region had been depolymerized, but in other regions of the cell they were apparently normal. We suggest that the depolymerization of microtubules affects nuclear movement by altering the tensile strength of the cytoplasm, and that cytoskeletal tension mediate nuclear positioning.We also found that accelerated nuclear movement could occur when most of the microtubules surrounding the nucleus were depolymerized. A comparison of the microtubule population surrounding the nucleus in unirradiated versus irradiated cells suggested that microtubules move with nuclei. Therefore, the nucleus does not appear to move via a direct interaction with microtubules.
Eukaryotic Cell, 2005
Candida albicansis an opportunistic fungal pathogen whose virulence is related to its ability to switch between yeast, pseudohyphal, and true-hyphal morphologies. To ask how long-distance nuclear migration occurs inC. albicanshyphae, we identified the fundamental properties of nuclear movements and microtubule dynamics using time-lapse microscopy. In hyphae, nuclei migrate to, and divide across, the presumptive site of septation, which forms 10 to 15 μm distal to the basal cell. The mother nucleus returns to the basal cell, while the daughter nucleus reiterates the process. We used time-lapse microscopy to identify the mechanisms by whichC. albicansnuclei move over long distances and are coordinated with hyphal morphology. We followed nuclear migration and spindle dynamics, as well as the time and position of septum specification, defined it as the presumptum, and established a chronology of nuclear, spindle, and morphological events. Analysis of microtubule dynamics revealed that p...
Bioscience, Biotechnology, and Biochemistry, 2005
Nuclear migration is indispensable for normal growth, differentiation, and development, and has been studied in several fungi including Aspergillus nidulans and Neurospora crassa. To better characterize nuclear movement and its consequences during conidiophore development, conidiation, and conidial germination, we performed confocal microscopy and time-lapse imaging on A. nidulans and Aspergillus oryzae strains expressing the histone H2B-EGFP fusion protein. Active trafficking of nuclei from a vesicle to a phialide and subsequently into a conidium provided the mechanistic basis for the formation of multinucleate conidia in A. oryzae. In particular, the first direct visual evidence on multinucleate conidium formation by the migration of nuclei from a phialide into the conidium, rather than by mitotic division in a newly formed conidium, was obtained. Interestingly, a statistical analysis on conidial germination revealed that conidia with more nuclei germinated earlier than those with fewer nuclei. Moreover, multinucleation of conidia conferred greater viability and resistance to UV-irradiation and freezethaw treatment.